There are mainly two different methods to do strength training and both have their inherent strengths and weaknesses. The first is to exercise with free weights and the second is to exercise with exercise machines that use cables to transfer the weight from a resistance source to a user.
The advantage of free weights is that they're very effective in producing strength gains and muscle mass. This is, in part, because the weight is unguided, and therefore secondary muscles get involved during the exercise in order to balance the weight. One of the inherent problems with free weights is that exercising with them is not as safe as exercising with an exercise machine. A lifter can lose his balance and be injured in a fall. The lifter may not be able to finish a lift, in which case he can become pinned under a bar. Plates can slide off the bar during a lift, potentially causing injury to the lifter and most likely to the floor. Lifting with free weights is also time consuming because of the need to take weight plates on and off to change the resistance, and because of the need to move the bar to different positions on the bar rack for different exercises. Also the lifting area can become cluttered with weight plates, thereby causing a hazard and making it difficult to locate desired weigh plates. In addition, some body parts are best worked out with an exercise machine, such as using a cable pulldown machine for working out the back. Furthermore, cost can be a factor. A lot of equipment is needed to be able to do a complete free weight workout, such as, the free weights, dumbbells, various lifting bars, a bench that inclines and declines, a bar rack for holding the barbell in several locations, and a cable pulldown machine. Purchase of all of this equipment can get quite expensive. Since free weights and free weight equipment are not designed to be compact or stored out of view, typically a whole room needs to be dedicated to such a setup.
Some of the advantages of exercise machines that make them so popular are that they overcome many of the disadvantages of free weights. They're safer to use than free weights as there is no risk of falling, of being trapped by the weights, or of having the weights fall off. Because the means of resistance is typically a weight stack where the weights are confined, the weights don't get scattered, lost, or dropped on the floor, and changing the amount of weight is quickly achieved by just changing the position of the selector pin. Many different exercises can be performed on one machine, and some exercise machines have multiple workout stations and weight stacks to permit performance of the various exercises needed for a complete body workout. Since it is possible to quickly and easily change between different exercises and resistance levels, circuit weight training is possible.
Circuit weight training was developed to promote both aerobic and muscular fitness at the same time. It consists of a series of exercises performed in succession, with a maximum of 30 seconds of rest between exercises, and lasting a total of 30 minutes. In order to maintain such a pace, an exercise machine must allow for a very quick and smooth transition between the different exercises and resistance levels, or there needs to be many different workout stations to allow all the different exercises needed to get a full body workout.
One of the problems with exercise machines is that they take up a lot of floor space. While some take up a smaller amount of floor space than others, typically they are all free standing and need to be set up far enough away from walls and furniture in order to allow for the space necessary to move around them and to exercise freely. Most exercise machines are designed such that only a certain number of body parts can be exercised per workout station. This is because the typical workout station is dedicated to doing specific exercises, such at a high pull station for doing pulldowns, or a low pull station for curls, or a station dedicated to doing the bench press or squats, etc. Exercise machines with multiple stations are larger machines that require more steel, pulleys, and parts, resulting in a more complicated and expensive exercise machine that takes up more floor space.
Some inventions have attempted to deal with the problem of dedicated workout stations by allowing the pull point to be adjustable in space. Some have achieved this by allowing the pull point to be adjusted vertically such as shown in U.S. Pat. Nos. 2,977,120; 4,402,504; 4,549,733; 4,603,855; 4,834,367 and 4,898,381. One of the problems to be overcome by doing this is what to do with the excess cable as the pull point is moved. Another method to adjust the pull point in space is to position the pull point at the end of an arm, which pivots from a fix point on the frame of the machine as shown in U.S. Pat. Nos. 4,826,157, 6,458,061 and 6,488,612. Cable length is constant but the arms pivot from a fixed pivot point.
Another problem with exercise machines is that during the performance of some of the pressing exercises or fly motion exercises, the path of travel for the exercise follows a predefined arc or guide-way. Such single plane motion eliminates or substantially reduces the amount of work that smaller secondary muscles would be required to do to balance the weight if the same exercise was being performed using free weight exercises.
Some machines require extra time in selecting a resistance level, especially those that utilize progressive resistance means such as springs, elastic band resistance, or flexible members to provide the resistance. These means of resistance are generally not as preferred by serious athletes for muscle development, who instead prefer the constant resistance offered by free weights or stack weight machines. If a machine takes a long time to be setup for different exercises and resistance settings, circuit training cannot be performed, and the workout is longer than otherwise needed.
Another problem with existing exercise machines is that they detract from a room that is not specifically dedicated for exercise. Most exercise machines aren't designed to be hidden from view when not in use, which can be unsightly for a room that is not specifically dedicated to be a fitness room. Some gyms are designed to fold up when not in use to cut down on the space they take up, but they're often too heavy and/or bulky to move or store away from view. There are some home gyms that fold up and can be stored out of sight, perhaps under a bed. But these require substantial time and effort to unfold for a workout and then fold up again afterwards. In addition, these fold-up gyms often fail to provide a full body workout.